Fix Dropwizard healthcheck.

The resource should only return unhealthy if the node is leading and
the scheduler is not running. For a standby node (not leading), the
scheduler can (and must!) be down.

Turns out no one seems to use that. :-)
Change MesosResourcesObject to be resource agnostic.

Replace hardcoded resources with generic code.
Refactor mesos scheduler delegator to actually delegate.

Factor out common code (locking etc), have real delegates to do the work.
wip
Finish factoring out the offer processor
wip